Anaesthesia: Uproar In Slumberland

20. February 2018

Media reports of intraoperative alertness have aroused uncertainty in patients. These include for example: "Problems during full narcosis – patients became restless during surgery". Anaesthetists feel assaulted by these reports. How great is the risk in actuality?

Patients still have serious concerns about doctors performing OPs which involve general anaesthesia. Among other things, the patients are afraid of ending up in an intraoperative waking state, ie. a state of awareness. In this situation the patient perceives his or her surroundings more or less clearly and can in retrospect partially recall the procedure. Media in Germany stoked new fears in mid-December. So what happened?

Intraoperative alertness

As University Hospital Magdeburg (Germany) reports, doctors noticed reflexive movements in three patients during anaesthesia induction using propofol. Shortly thereafter, they adjusted the dose. Further problems did not occur. Contact made with the pharmaceutical manufacturer remained unfruitful. “B. Braun was informed at the time that patients woke up when given a dose of propofol”, a spokeswoman for the hospital says. “We then checked the batch documentation and found no irregularities”. And the relevant Ministry of Science responded to queries, stating that no discernible misconduct was picked up.

Prof. Dr. Thomas Hachenberg, Director of the Department of Anaesthesiology and Intensive Therapy at University Hospital Magdeburg, adds: “Intraoperative wakefulness is a very rare phenomenon, albeit a very distressing event for the patient”. Data shows that frequency ranges from one or two cases per 1,000 anaesthetisations to one case per 19,000 anaesthetisations. With children, however, the risk is eight to ten times higher, Professor Petra Bischoff from the Ruhr University Bochum (Germany) reports.

Possible risk factors include muscle relaxants, unscheduled interventions, cardiac surgery and paraplegia events, as well as drug abuse. People who according to risk classification fall into categories IV (patients with life-threatening illness) or V (moribund patients who are unlikely to survive without surgery) also significantly more frequently experience intraoperative wakefulness. What can doctors do to stop this?

Experts from the American Society of Anesthesiologists recommend the isolated forearm technique (IFT). Before administering muscle relaxants, a tourniquet is applied to the upper arm so that the forearm can still be moved consciously. The patient is regularly asked via headphone to move in the instance of awareness. Robert D. Sanders of the University of Wisconsin-Madison found out that 4.6 percent of all patients under general anaesthesia responded to IFT. His cohort included 260 patients.

Technical systems could be an alternative to the IFT in the medium term. Algorithms employed as part of entropy monitoring or bispectral index analyse irregularities in the EEG signal. All methods currently have their limitations when used on very old patients, when using ketamine or laughing gas.

Expulsion of gastric contents

Far more dangerous than awareness during an OP is the expulsion of stomach contents. According to British data it is the most common fatal anaesthetic complication. This is reason enough for German professional societies to formulate recommendations:

Small meals such as a slice of white bread with jam or a glass of milk are allowable up to six hours before the induction of anaesthesia.

Clear liquids, ie. drinks without suspended solids and emulsified fat particles, can be drunk in small amounts up to two hours before the start of anaesthesia. These include, for example, tea or coffee. Unsuitable drinks include turbid liquids such as those containing milk or fruit pulp particles.

Oral medications may be taken with a sip of water until a point of time just before the procedure.

Newborns and infants may be breastfed up to four hours before induction of anaesthesia.

The possible risk of expulsion being increased by smoking cigarettes is largely negligible.

Birgit Larsen from the University of Aarhus delivers new arguments against differentiating between clear and cloudy liquids. She gave healthy subjects coffee with or without milk. After two hours, she ascertained gastric volume by MRI, without finding any significant differences. “The results support freely using milk in hot drinks prior to planned anaesthesia”, Larsen notes.

Waking delirium

Complications may occur even after the procedure has been carried out. Postoperative delirium goes hand in hand with a diversity of disturbances involving consciousness, attention and orientation. Patients have to be cared for longer in hospital. Sometimes they cause self-injury and decide to remove their catheters. Incidence varies from 5 to 15 percent in elderly patients and from 10 to 80 percent with children.

US anaesthetists employ ketamine bolus doses in adults, their reasoning being based on results of animal experiments and a Cochrane review, among other studies. Michael S. Avidan, based on the results of his randomised, double-blinded study, raises doubts about this practice. He randomised 672 patients in three groups: 0.5 mg/kg ketamine, 1.0 mg/kg ketamine, and placebo. Surprisingly, 20 or 28 percent of those in the verum group hallucinated, compared to 18 percent of those who had only been given the pretend medication. Avidan therefore urges that current practice be reconsidered.

The situation looks better for clonidine use after general anaesthesia using sevoflurane and fentanyl. Mogens Ydemann from the University of Copenhagen included 379 children between one and five years of age in her study. They received either clonidine or saline intraoperatively. In the verum group, wake-up delirium was much less common than with placebo, namely 25 versus 47 percent.

Increased mortality

If the patient wakes up, further dangers threaten over the subsequent few days or weeks. Even in the absence of any irregularities, myocardial damage and markedly increased mortality occur following non-cardiac procedures. Two research groups independently of one another have now shown that troponine is suitable as a marker. These proteins enter the bloodstream, should cardiac muscle cells be damaged.

Philip J. Devereaux from McMaster University in Hamilton, Canada, evaluated data from 21,842 patients for an observational study. The patients were on average 63 years old and were operated for varied reasons. Cardiological indications were not among these reasons. As Devereaux reports, there were associations between the perioperative level of highly sensitive troponine T (hsTnT) and 30-day mortality. Mortality was 0.5 percent for less than 20 ng/l, 3.0 percent for 20 to 65 ng/l, 9.1 percent for 65 to 1,000 ng/l, and 29.6 percent for even higher levels.

These results were confirmed by Christian Puelacher from University Hospital Basel using a cohort of 2,018 patients. In 397 out of 2,546 operations he detected myocardial damage based on hsTnT values. 30-day and one-year mortality rates were significantly elevated in this group (9.8 versus 1.6 percent and 22.5 versus 9.3 percent, respectively). Neither Devereaux nor Puelacher currently see a possibility of intervening.

Brain development

Dangers lurk not only for older, multimorbid patients. General anaesthesia possibly harming brain development at a young age is a controversial point. Looking at young animals, many drugs show neurotoxic potential: this finding is only relevant with regard to humans to a limited extent. Experts from the US Food and Drug Administration come to the conclusion that “a single, relatively short exposure to narcotics and sedatives in infants or toddlers is unlikely to have adverse effects on behaviour or learning”.

The basis of their recommendation is among others a study by Andrew J. Davidson, Melbourne. He separated a total of 722 children who had to undergo surgery within 60 weeks of their birth into either a localised anaesthesia group or a sevoflurane-based general anaesthesia group. There were no significant differences in cognitive development at the age of two years. In addition the PANDA study (“Paediatric Anaesthesia NeuroDevelopment Assessment”) revealed no irregularities. In this cohort, doctors compare sibling pairs who had and had not had general anaesthesia in the course of their development.

A Swedish register study involving 33,514 children shows small but significant associations. The subjects had been given various levels of general anaesthetic agents sometime until their fourth birthday. Using a measure based on school grades, the difference was 0.41 percent (one general anaesthetic), 1.41 percent (two general anaesthetics) and 1.82 percent (three or more general anaesthetics). The study provides indicators but cannot demonstrate causality. And last but not least Robert I. Block of the University of Iowa found MRI based indications that early general anaesthesia leads to a significantly reduced total white matter of 1.5 percent. All cohort studies ultimately prove no causality.

Rarely serious events

The bottom line is that anaesthetics are safe by professional standards today. The last study with a broad database was released in 2014. Dr. Dr. Jan-H. Schiff from Klinikum Stuttgart (Germany) together with colleagues evaluated data on 1.36 million anaesthetic events in Germany. In 36 cases serious complications occurred. An expert team clearly attributed ten events to anaesthesia. Thus, fatal complications from anaesthesia itself occur in at least one out of 140,000 patients.